Sampler albums have been a hip-hop staple since the genre's inception, and their diversity is illustrated nicely by three recent albums: Hip Hop 101, No More Prisons, and World Wrestling Federation: Aggression. Aggression is the latest installment in what has become a miniature cottage industry of wrestling-themed hip-hop compilations celebrating the theatrical aggression and love of brute force that unites hip-hop and the colorful world of pro wrestling. It's become something of a cliché for these compilations to pair rappers with thrashing guitars (the idea being that heavy metal makes hip-hop less threatening and more familiar to blue-collar white audiences), and Aggression is no exception. Largely produced by frequent Mack 10 collaborator Binky with meat-and-potatoes skill but little sonic diversity, Aggression features a slew of major hip-hop acts adapting the theme songs of some of the WWF's most popular grapplers. The pairing of über-eccentrics Kool Keith and Ol' Dirty Bastard on "Wreck" is a predictably loopy highlight, but it's more than matched by the inspired pairing of lesser-known but no less gifted eccentrics Ras Kass and Mystikal on the Triple-H-themed "Game." The less notable pairing of No Limit soldiers C-Murder and Magic yields a cheesy slice of horror-core so over-the-top that it approaches so-bad-it's-good territory on the Gangrel theme "I Won't Step," but big-name entries from Snoop Dogg & W.C. and Ice-T fail to make an impression. Perhaps Aggression's biggest surprise is Bad Azz and Techniec's "You Ain't Hard," an inspired take on the New Age Outlaws theme that proves an unexpected highlight. Far more ambitious, but equally solid, is Hip Hop 101, an underground sampler executive-produced by De La Soul. With styles ranging from the vocal strong-arming of Likwit associate Defari to the bad-seed antics of Eminem compatriot Royce The 5'9", to the urgent flow of Black Star's Talib Kweli, Hip Hop 101 offers a winning overview of underground hip-hop's present and future. Surprisingly, some of Hip Hop 101's weakest moments come courtesy of De La Soul itself: "So Good" is undermined by lazy, uninspired production, as is Maseo of De La Soul's "Words & Verbs," a limp track that reinforces just how integral the production genius of Prince Paul was to the group's success. As with Aggression, the highlight of Hip Hop 101 comes from an unlikely source: newcomer The Bad Seed, whose quirky, skeletally produced "Pockets" sounds like "Guilty Conscience" re-imagined by The Mountain Brothers. Solid and eclectic, the collection should appeal to its target audience, but it's accessible enough to appeal to the uninitiated, too. Even better is the anti-prison benefit album No More Prisons, a leftist compilation whose title clearly lays out its political agenda. A multi-artist sampler more cohesive and direct than most solo albums, No More Prisons paints a vivid, impassioned portrait of a world in which the spread of prisons isn't a vague social issue but a day-to-day reality in every corner of working-class life. From Dead Prez's dark, hypnotic "Behind Enemy Lines" (also featured on the group's terrific debut album, Let's Get Free) to the irreverent yet impassioned space-age funk of The Coup's "Drug Warz," No More Prisons possesses undeniable gravity and a palpable sense of urgency. Yazeed's "Underground Railroad" draws a link between the exploitation and captivity of slavery and prison life, illustrating the expansive worldview that gives the collection much of its power. No More Prisons is multi-focused in its attack, taking on not only the prison-industrial system that exploits the labor of prisoners, but also the poverty and racism that have made America the world's leader in building new prisons while imprisoning an ever-larger percentage of its underclass. In a time in which the vast majority of hip-hop aims at delivering instant gratification at any cost, it's encouraging to hear No More Prisons, which aims high in an attempt to bring about lasting social change.